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Plasma cleaning instrument Atmospheric pressure DIELECTRIC barrier discharge plasma

Plasma cleaning instrument Atmospheric pressure DIELECTRIC barrier discharge plasma

Dielectric barrier discharge (DBD), referred to as DBD discharge, is a kind of gas discharge with insulating medium inserted between discharge electrodes. The medium may be overlaid on the electrode or suspended in the discharge space. In this way, when a high enough ac voltage is applied to both ends of the electrode, the gas between the electrodes can be broken down under high pressure, forming a so-called DBD discharge. The plasma washer discharge is similar to glow discharge, which is uniform, diffuse and stable. It is actually composed of many small fast pulse discharge channels. Generally, the pressure of discharge gas can reach 1 ATM (1 ATM = 1.013X 10^5 Pa), so DBD discharge belongs to non-thermal equilibrium discharge under high pressure, which is also known as silent discharge.   The common DBD discharge device of plasma cleaning instrument is usually composed of two parallel electrodes, and at least one electrode is covered by dielectric material. In order to ensure the stability of discharge, the two electrodes are spaced at several millimeters apart, and sinusoidal or pulsed high-voltage power supply is needed to realize atmospheric discharge. DBD discharge reactor consists of three parts: high voltage electrode, electric dielectric and ground electrode. The structure of single-gap single-dielectric barrier discharge reactor is characterized by that the dielectric is connected with the high-voltage electrode and the discharge area is between the grounding electrode and the dielectric. The structure is simple and is often used to produce ozone. Double gap single dielectric barrier discharge reactor is characterized by two different reaction zones formed between the upper and lower electrodes of the plasma cleaning apparatus and the medium, which are generally used to produce plasma with two different components. The structure of single-gap dual-dielectric barrier discharge reactor is characterized by the fact that the reaction takes place between two layers of dielectric, so as to avoid the influence of electrodes on the reaction, especially for corrosive gases and the reaction that needs to produce high-purity plasma in a closed environment. This structure has outstanding advantages. In addition to parallel plate structure, DBD discharge device also has line simple structure and surface structure.   Atmospheric DBD discharge plasma usually presents filament discharge or glow discharge characteristics. When high pressure is applied at both ends of the electrode, the gas near the cathode ionizes under the action of electric field to produce electrons. These electrons accelerate in the electric field before the gas is completely broken down. When the energy reaches or exceeds the ionization energy of the gas, the electrons multiply in each ionization collision and form an electron avalanche. Electrons are more mobile than ions, allowing them to pass through gas gaps in the measurable nanosecond range. When the electron avalanche is formed in the gas gap and generates directional movement, ions will be trapped behind due to slow movement speed and will form accumulation in the discharge space. The generation of space charge distorts the electric field in the discharge space, so that the electric field intensity of the air gap between electrodes equals or exceeds the breakdown field intensity of the surrounding gas. Therefore, the gas ionization increases sharply in a short time, leading to the occurrence of a single filament discharge.   A single filamentation discharge occurs at one location in the discharge gas gap and at other locations at the same time. It is the insulating nature of the medium that enables this filament discharge to occur independently in many discharge Spaces. When the voltage at both ends of the filamentous discharge is lower than the breakdown voltage, the current is cut off. Only when the breakdown voltage is reached again at the same position can the plasma cleaner re-breakdown and a second filameter discharge occur at the original place. Each filamentous discharge is only a few dozen to a few hundred nanometers in diameter, and the roots of these filaments are attached to the dielectric layer and create bumps and bumps on the surface. The existence of concave-convex points on the surface of the dielectric layer increases the local electric field intensity and makes the discharge more likely to occur, which is commonly referred to as the cusp discharge. A micro-discharge process is actually a process in which streamer discharge occurs and disappears. The so-called streamer discharge is a discharge phenomenon in which a local area of the discharge space is highly ionized and rapidly transmitted. In DBD discharge, it is usually divided into three stages: discharge breakdown, streamer development and discharge disappearance.   As a simple and easy to operate atmospheric pressure

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Plasma surface modification equipment for medical devices

Plasma surface modification equipment for medical devices

Another important application of plasma surface modification equipment is to promote cell growth or protein binding, thereby reducing thrombus formation. The polytetrafluoroethylene coating and organosilicone monomer have blood compatibility. The fluorocarbon ratio (F/C ratio) and the presence form of wettability in the film are obviously closely related to the absorption and storage of fibrinogen, a protein in the blood that participates in the coagulation process of blood. PECVD can be used to prepare polytetrafluoroethylene films with different surface morphology.   Silane - like films can be obtained by plasma polymerization of organosilicon monomer. The SiCHO compound was applied to the blood filter and the hollow fiber membrane of polypropylene to coat the activated carbon particles. Hemoperfusion device is to circulate the blood of the patient's artery into the hemoperfusion device, so that the poisons and metabolites in the blood are adsorbed and purified, and then injected back into the body. The absorbent of hemoperfusion apparatus mainly includes activated carbon, enzyme, antigen and antibody, etc. The carbon particles must be coated with a polymer film to prevent fine particles from entering the blood. Similarly, the microporous polypropylene blood oxygenator needs to be coated with a silane polymer film to reduce the roughness of the polypropylene surface and thus reduce damage to blood cells.   Heparin and heparin-like molecules, collagen, albumin, and other life-giving molecules can be fixed on the surface of the polymer and act as antithrombotic agents. So to fix these molecules to the surface of the polymer, you need to activate the polymer and respond to the grafted molecules. This process mainly adopts the experimental and empirical method, and the graft base groups used are mostly NH3, OH and -COOH, which are mainly obtained from raw materials supplied by non-precipitation. Amino functional groups appear on the surface of materials treated by ammonia gas plasma, which are similar to liver phosphorus ester and can be used as attachment points of anticoagulants. Examples of this kind of plasma used in vitro medical utensils include cleaning and modification of petri dishes for experiment or drug production, and surface modification of microporous plates. The surface modification can also improve the biocompatibility of human implants. For example, the biocompatibility of artificial blood vessels, contact lenses and drug delivery implants could be improved by improving the adhesion of blood-capacity coatings to materials. In some applications, such as contact lenses and intraocular lens materials, surface treatments can also reduce protein or cell adhesion.   Many materials encourage proteins to bind, leading to the formation of blood clots. Anticoagulant coating can effectively reduce surface clotting and thrombosis, but antithrombotic materials often cannot be well combined with polymer surface. The active free radicals in plasma were used to enhance the effective chemical bond on the surface of the material through heparinization or grafting of antithrombolytic groups. The effect of material surface modification depends on a number of factors, including the choice of material matrix, composition of antithrombotic coating, and service life of the modified material. Animal experiments showed that the plasma-activated modified polyurethane catheter showed no protein attachment after 30 days of use. The plasma-activated polyurethane catheter without heparin coating showed a small amount of protein attachment. There was serious thrombus in the fluid guide tube without plasma surface modification. Compared to the untreated blood filter, the improved blood filter can significantly reduce the amount of platelet adhesion.

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Plasma chemical reaction in plasma cleaning machine

Plasma chemical reaction in plasma cleaning machine

The chemical reaction initiated by plasma of plasma cleaning machine can be described as the following three stages. Plasma production stage, in which a large number of electrons and ions with higher energy are produced; At the activation stage of reactive molecules, high-energy electrons in the plasma collide with reactive molecules, thus causing changes in the internal energy of reactive molecules and causing excitation, dissociation and ionization of reactive molecules. The stage of product formation, in which the reactive species produced by excitation, dissociation, and ionization of reactive molecules are unstable and various chemical reactions take place between them to produce reaction products. Chemical reactions in plasma can be divided into homogeneous reaction, polyphase reaction and photochemical reaction.

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Medical applications of plasma-activated treatment equipment

Medical applications of plasma-activated treatment equipment

In some cases, surface modification and activation of cultured cells are necessary to improve cell adhesion and cell growth rate. Under special conditions, cell adhesion was a necessary condition to ensure cell proliferation, and the cell proliferation rate of the culture dish treated by plasma activation equipment was significantly higher than that of the untreated culture dish. The results show that the modification and activation of polyester, polyethylene and K resin by plasma can significantly improve their adhesion properties.   Compared with other materials, the surface friction coefficient of polymers such as silicone and polyurethane is higher. After plasma surface activation treatment, the instrument made of this material is coated with a layer of polymer with low friction coefficient to make its surface more lubricated. For example, after plasma surface activation, the adhesion of hydrogel coating on the surface of medical catheter can be improved, thus reducing the friction between the medical catheter and the blood vessel wall. Catheters for the urethral, respiratory, tracheal, and cardiovascular systems, or instruments for endoscopic/laparoscopic surgery, and ophthalmic materials, when in contact with body fluids, have a good hydrophilic properties, so that when body fluids come into contact with the surfaces of these smooth medical devices, they do not stick to their surfaces. Plasma ionized gases can reduce this friction coefficient on the surface. Small friction coefficient of medical devices, when inserted or removed from the patient's body, can reduce the mechanical damage to the patient's mucosa, reduce the patient's discomfort. Plasma technology in combination with other technologies, especially xylene polymer coating, has been successfully used in the manufacture of a variety of medical devices, such as ophthalmology and imaging surgery.   Film deposition method is used to deposit a barrier layer on the surface of plastic products to reduce the permeability of liquid such as alcohol to the surface of plastic products. For example, treating high-density polyethylene (HDPE) with plasma-activated equipment reduces the material's permeability to alcohol by a factor of 10. Due to the interaction between blood and certain chemical components in biological materials, blood clotting can be caused and human health is jeopardized. Therefore, implants made of biological materials such as silicone rubber, polyester, polytetrafluoroethylene, polyurethane and PVC can only stay in the blood for a short time. For example, dioctyl phthalates (DOP) and certain stabilizers in PVC blood bags are slowly released from the PVC base and react with the blood, causing blood to clot. After plasma treatment of PVC material, a cross-linked film is formed on the surface. The film is biocompatible, which can adjust the dispersion degree of the film within a small range and play a role in controlling the transmission of substances such as stabilizer.   Plasma-modified and activated membrane materials can improve the selectivity of diffused materials. Generally, it is necessary for membrane materials to have high permeability and high selectivity to permeable materials. By controlling the pore size and combining with chemical action or physical restriction, the membrane surface selectivity can be improved, which is beneficial to the application of biological separation process in hemodialysis and protein purification.   In general, diagnostic biosensors often require biological components such as enzymes or antibodies to be fixed to the surface of the sensor. Plasma grafting and surface functional activation treatment provide a convenient and effective method for establishing covalent bonding between biological components and substrates.

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Atmospheric pressure plasma cleaning ritualistic reaction process diagnosis technology

Atmospheric pressure plasma cleaning ritualistic reaction process diagnosis technology

Atmospheric pressure plasma is an important technology for energy gas conversion, material preparation and surface modification, environmental protection and biomedicine. There are many process variables in plasma, such as plasma temperature, density, various active species, etc., which affect the interaction between plasma and reaction medium and determine the structure and properties of reaction products or materials. The plasma temperature, density and various active species depend on the macroscopic parameters and conditions of the plasma, such as pressure, power and gas flow rate. Therefore, the diagnosis of plasma process is helpful to obtain the micro-mechanism of plasma discharge, establish the correlation between plasma process parameters and the results of plasma reaction, and find the internal information between them, so as to realize the controllability of plasma process.   Cleaning instrument plasma diagnosis technology is divided into off-position technology and in-situ technology. The offsets technique involves the extraction of plasma samples from a plasma reactor, such as mass spectrometry and gas phase electron paramagnetic resonance. The in-situ technology of atmospheric pressure plasma cleaning instrument includes invasive and non-invasive diagnostic techniques: invasive diagnostic techniques disturb the plasma, such as probe technique; The perturbation of plasma by non-invasive diagnostic techniques, such as spectroscopic diagnostic techniques, can be ignored. In atmospheric pressure plasma, spectral diagnosis is a common diagnostic technique.   Spectroscopic diagnosis technology is an important means to diagnose the complex physical and chemical processes occurring in the plasma and to measure the plasma temperature. It has the advantages of simple operation, good selectivity, high sensitivity and accuracy and no interference to the plasma. Spectroscopic diagnostic techniques mainly include emission spectrometry, absorption spectrometry and laser induced fluorescence.   OES is a common method to monitor and diagnose plasma processes. The spectral features of the emission spectrum provide rich information about the chemical and physical processes in the plasma. By measuring the wavelength and intensity of the spectral lines, various ions and neutral groups in the plasma can be identified.   The emission spectrum of atmospheric pressure plasma cleaning instrument can be divided into linear spectrum, banded spectrum and continuous spectrum, which are mainly used in the diagnosis of plasma emission spectrum. The atomic spectrum is generally linear, for example, the spectrum of hydrogen atom is simple atomic spectrum, it has mutually independent spectrum, only one line in the visible region, namely the Balmer line, the brighter four lines are: Hα-656.28 nm，Hβ-486.13 nm，Hγ-434.05 nm， Hδ-410.18 nm.

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Plasma etching machine process introduction

Plasma etching machine process introduction

Plasma etching machine etching can be divided into two processes: first, the chemical active components of the plasma, these active components react with solid material substances, produce volatile compounds, and diffuse to the surface, discharge. Take CF4 as an example, its dissociation F reacts with S to form SiF4 gas, forming micro-milling structure on the surface of Si material. Plasma etching refers to ion etching, sputtering etching and plasma ashing.   The modification depth of plasma etcher depends on the substrate temperature, treatment time and material diffusion characteristics, while the modification type depends on the substrate and process parameters. Plasmas can only be etched a few microns deep on the surface and the surface properties change, but the surface properties of most materials can be maintained. The technology can also be used for surface cleaning, curing, coarsening, changing hydrophilicity and adhesion, etc., as well as for the manufacture of semiconductor integrated circuits, where sample thinning can be observed under an electron microscope. Chemical reactions can produce volatile products by chemical sputtering. Common gases include Ar, He, O2, H2, H2O, CO2, Cl2, F2 and organic vapour. Inert ion sputtering is closer to the physical process than plasma sputtering with chemical reaction.   Plasma F etching Si is widely used in semiconductor equipment manufacturing. The three steps of etching reaction are as follows: Chemical adsorption: F2→F2 (ADS) →2F (ADS) Reaction: Si+4F (ADS) →SiF4 (ADS) Desorption: SiF4 (ADS) →SiF4 (GAS)   In the etching process, the high-density plasma source has many advantages, such as more accurate control of workpiece size, higher etching rate and better material selectivity. The high density plasma source can work under low voltage, so the oscillation of sheath can be weakened. In the process of chip etching, plasma source etching with high density is used, and independent rf source is needed to bias the wafer, so that energy and ions are independent of each other. Since the energy of ions is generally in the order of several electron volts, when ions enter the negative sheath, they will reach hundreds of electron volts through energy acceleration and have high directivity, thus making ion etching anisotropic.

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